1. Field of the Invention
The present invention relates to a type of monolithic microwave integrated circuit (MMIC) in which a waveguide for high frequency signals is used.
2. Description of the Related Art
For an MMIC which uses high speed semiconductor elements such as high-electron-mobility transistors (HEMTs) and hetero-bipolar transistors (HBTs), it is necessary to use a high frequency waveguide as a wiring line differently from an ordinary silicon integrated circuit because the MMIC processes high frequency signals. A microstrip line which has stable line characteristics and weak dispersion characteristics which means that frequency dependency of a transmission constant is weak, is used as the high frequency waveguide.
Among MMICs in which microstrip lines according to the related art are used, particularly so-called a xe2x80x9cthree-dimensional multilayered MMICxe2x80x9d in which a line conductor is multilayered is shown in FIG. 1.
As shown in FIG. 1, the multilayered MMIC has a ground plate 3 provided on a surface insulating layer 2 formed on a semiconductor substrate 1. The ground plate 3 combines with line conductors 5 provided on insulating interlayers 4 to form microstrip lines. A pad 6 is provided on the top insulating interlayer 4 and is connected to the exterior.
The MMIC in FIG. 1 is accommodated in a predetermined package and is wire-bonded to the pad 6 so that its potential is connected to the exterior.
The MMIC processes a high frequency signal, and electromagnetic waves outside the chip of the MMIC may affect the operation of the MMIC. Accordingly, in general, the chip is accommodated in a package the inside of which is electrically shielded.
A metal package or a ceramic package which is known as a package in which the chip is accommodated in electrically shielded condition is expensive. Also, when a plurality of elements are accommodated in a single package, mutual interference caused by electromagnetic waves emitted from the elements must be prevented.
It is an object of the present invention to provide an MMIC which reduces interference caused by external electromagnetic waves or leakage of electromagnetic waves to the exterior.
To this end, according to the present invention, the above object is achieved through provision of a high frequency semiconductor device including a semiconductor substrate, a ground plate connected to the ground potential, at least one insulating interlayer, a line conductor provided above the ground plate, with the at least one insulating interlayer provided therebetween, at least one terminal for connecting to the exterior, and a shield plate which is provided above the highest layer of the line conductor, with the at least one insulating interlayer provided therebetween and which is connected to the ground potential.
Preferably, the at least one terminal is a wire-bonding pad.
The shield plate may have an opening in an area in which the wire-bonding pad is positioned.
The wire-bonding pad may be provided on the shield plate.
The shield plate may substantially cover the entirety of the semiconductor substrate.
The high frequency semiconductor device may further include a plurality of throughholes which are formed in the periphery of the shield plate so as to surround an inner area excluding the periphery and which reach the ground plate, and internal conductors provided in the throughholes, the internal conductors connecting the shield plate and the ground plate.
The at least one terminal may lead from the back of the semiconductor substrate.
The at least one terminal may be connected to the surface of the semiconductor substrate by a viahole penetrating the semiconductor substrate.
The at least one terminal may be a flip chip pad.
The semiconductor substrate may be divided into an element-arranged area in which semiconductor elements are formed and an outer area around the element-arranged area in which at least one terminal is provided, and the shield plate may selectively cover the element-arranged area.
The high frequency semiconductor device may further include a plurality of throughholes which are formed in the periphery of the shield plate so as to surround an inner area excluding the periphery and which reach the ground plate, and internal conductors provided in the throughholes, the internal conductors connecting the shield plate and the ground plate. The at least one terminal and the element-arranged area may be made in conduction by an area in which the throughholes are not provided.
The terminal may be an antenna.
The shield plate may have an opening in a portion corresponding to the antenna.
A terminal for electrically connecting to the exterior may be further provided on the back of the semiconductor substrate.
The terminal may be connected to the surface of the semiconductor substrate by a viahole penetrating the semiconductor substrate.
The terminal may be a flip chip bonding.
The ground plate may be used as an antenna grand plane in the antenna.
The antenna may be provided on the shield plate, and the shield plate may be used as an antenna grand plane.
The antenna may be a patch antenna.
The at least one insulating interlayer may be made of one of polyimide and benzocyclobutene.
According to the present invention, interference caused by external electromagnetic waves or leakage of electromagnetic waves can be reduced in a chip alone because the surface of an MMIC is shielded by a shield plate. Accordingly, simplified packaging can be performed, and a chip according to the present invention can be mounted on a circuit board, or the like.